Acid cleaners for metal substrates and associated methods for cleaning and coating metal substrates

ABSTRACT

Disclosed are methods for cleaning and coating metal substrates, and the coated substrate formed therein, that include contacting the substrate with an acid and then contacting the cleaned substrate with an electrodepositable coating composition comprising a film forming polymer and a corrosion inhibitor.

FIELD OF THE INVENTION

The present invention relates to acid cleaners for metal substrates andassociated methods for cleaning metal substrates with the acid cleanersprior to application of a pretreatment composition and/or anelectrodepositable coating composition.

BACKGROUND INFORMATION

The use of protective coatings on metal substrates for improvedcorrosion resistance and paint adhesion is common. Conventionaltechniques for coating such substrates include techniques that involvepretreating the metal substrate with a pretreatment composition and/orwith an electrodepositable coating composition.

SUMMARY OF THE INVENTION

In certain embodiments, the present invention is directed to a methodcomprising: (a) contacting a substrate with an acid; and then (b)contacting the substrate with an electrodepositable coating compositioncomprising (i) a film-forming polymer; and (ii) a corrosion inhibitor;with the proviso that the method does not comprise contacting thesubstrate with a pretreatment composition prior to step (b).

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

Certain embodiments of the present invention are directed to methods forcleaning a substrate by contacting the metal substrate with an acid.

The acid cleaned substrate, in certain embodiments, may then becontacted with a pretreatment composition. In certain of theseembodiments, the pretreatment composition includes a group IIIB and/orIVB metal compound, wherein the citric acid cleaner acts to provideincreased deposition of the group IIIB and/or IVB metal onto the metalsubstrate surface, wherein the increased metal content acts to improvecorrosion resistance.

In certain other embodiments, a film forming composition, such as anelectrodepositable coating composition, may be applied over the acidcleaned and optionally pretreated substrate. In these embodiments, theacid provides improved corrosion protection to the coated substrate ascompared with coated and uncleaned substrates or substrates cleaned withalkaline cleaners and coated as described above.

In certain other embodiments, a film forming composition, such as anelectrodepositable coating composition, may be applied over the acidcleaned substrate without first contacting the substrate with apretreatment composition. In certain of these embodiments, the acid actsto improve corrosion resistance of these acid cleaned and electrocoatedsubstrates as compared with coated and uncleaned substrates orsubstrates cleaned with alkaline cleaners and electrocoated as describedabove.

Each of these embodiments is described below:

Substrate

Suitable substrates that can be cleaned and coated in accordance withthe present invention include, without limitation, metal substrates,metal alloy substrates, and/or substrates that have been metallized,such as nickel plated plastic. In some embodiments, the metal or metalalloy can be aluminum and/or steel. For example, the steel substratecould be cold rolled steel, electrogalvanized steel, and hot dippedgalvanized steel. Moreover, in some embodiments, the substrate maycomprise a portion of a vehicle such as a vehicular body (e.g., withoutlimitation, door, body panel, trunk deck lid, roof panel, hood, and/orroof) and/or a vehicular frame. As used herein, “vehicle” or variationsthereof includes, but is not limited to, civilian, commercial, andmilitary land vehicles such as cars, motorcycles, and trucks.

Cleaning

In certain embodiments, the substrates may be contacted with an acidprior to contacting the substrate with a pretreatment composition and/oran electrodepositable coating composition.

While not wanting to be bound by any theory, it is believed that theacid etches the substrate to provide increased surface area to thesubstrate. Increased surface area is believed to provide improvedadhesion between the substrate and the subsequently applied coatingmaterials, which is believed to improve corrosion resistance to thecoated panels. In addition, increased etching of the substrate materialis believed to allow for increased deposition of metal from thepretreatment composition, when utilized, which also is believed toincrease corrosion resistance to the coated panels. Further, increasedetching of the substrate material is believed for increased depositionof metal from the electrodepositable coating composition, when utilized,at the interface between the electrodepositable coating composition andthe substrate, which may provide even more corrosion resistance to thecoated panels.

In certain embodiments, the acid comprises a single acid, while in otherembodiments the acid comprises a mixture of acids.

In certain embodiments, the acid comprises a weak acid, while in otherembodiments the acid comprises a strong acid. A weak acid, bydefinition, is an acid that dissociates incompletely (i.e. it does notrelease all its hydrogens in solution), while a strong acid is an acidthat ionizes completely in an aqueous solution (i.e. which release allof their hydrogen atoms when dissolved in water).

In still other embodiments, the acid comprises an organic acid. Anorganic compound, by definition, is an organic compound having acidicproperties. Exemplary organic acids include uric acid, sulfonic acid,and carboxylic acids including lactic acid, formic acid, citric acid,and oxalic acid, as well as mixtures thereof.

In still other embodiments, the acid comprises a mineral acid. A mineralacid, by definition, is an acid derived from an inorganic compound.Exemplary mineral acids include hydrochloric acid, sulfuric acid, boricacid, phosphoric acid, hydrofluoric acid, hydrobromic acid, nitric acid,and mixtures thereof.

In still other embodiments, the acid may comprise any combination of oneor more organic acids and/or mineral acids.

In certain of these embodiments, the carboxylic acid selected for use inthe compositions described herein has a water solubility of >1 g/L at20° C. Carboxylic acids suitable for use include, for example,monocarboxylic acids, such as formic acid, acetic acid, propionic acid,methylacetic acid, butyric acid, ethylacetic acid, n-valeric acid,n-butanecarboxylic acid, acrylic acid, propiolic acid, methacrylic acid,palmitic acid, stearic acid, oleic acid, linolic acid, and linolenicacid; dicarboxylic acids, such as oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, lepargilic acid, sebacic acid, maleic acid, and fumaric acid;aliphatic hydroxy acids, such as glycolic acid, lactic acid, tartronicacid, glyceric acid, malic acid, tartaric acid, citramalic acid, citricacid, isocitric acid, leucine acid, mevalonic acid, pantoic acid,recinoleic acid, ricinelaidic acid, cerebronic acid, quinic acid, andshikimic acid; aromatic hydroxy acids, such as salicylic acid, creosoteacid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid,protocatechuic acid, gentisic acid, orsellinic acid, gallic acid,mandelic acid, benzilic acid, atrolactinic acid, melilotic acid,phloretic acid, coumaric acid, umbellic acid, caffeic acid, ferulicacid, and sinapic acid. Mixtures of any of the foregoing may also beused.

In certain embodiments, the acid is incorporated into an acid cleanerthat also may include other components such as water, surfactants and/orbuffers, including commercially available surfactants and/or buffers.

In certain other embodiments, the substrate to be treated in accordancewith the methods of the present invention may first be cleaned to removegrease, dirt, or other extraneous matter. This is often done byemploying mild or strong alkaline cleaners, such as are commerciallyavailable and conventionally used in metal pretreatment processes.Examples of alkaline cleaners suitable for use in the present inventioninclude Chemkleen 163, Chemkleen 177, Chemkleen 2010LP and Chemkleen490MX, each of which are commercially available from PPG Industries,Inc. In certain embodiments, a surfactant may also be included in thealkaline cleaner, such as 181LP, commercially available from PPGIndustries, Inc. Such cleaners are often followed and/or preceded by awater rinse. After cleaning, the bare substrate materials may be rinsedthoroughly with deionized water.

In certain of these embodiments, the alkaline cleaner is applied to thesubstrate prior to the acid cleaner, while in other embodiments the acidcleaner is applied to the substrate prior to the alkaline cleaner.

Pretreatment

In certain embodiments of the methods of the present invention, afterthe substrate is contacted with the acid, it may then be contacted witha pretreatment composition. As used herein, the term “pretreatmentcomposition” refers to a composition that upon contact with a substratereacts with and chemically alters the substrate surface and binds to itto form a protective layer.

In certain other embodiments of the present invention, the pretreatmentcomposition comprises a group IIIB and/or IVB metal compound.

In certain embodiments, the pretreatment composition comprises acarrier, often an aqueous medium, so that the composition is in the formof a solution or dispersion of a group IIIB or IVB metal compound in thecarrier. In these embodiments, the solution or dispersion may be broughtinto contact with the substrate by any of a variety of known techniques,such as dipping or immersion, spraying, intermittent spraying, dippingfollowed by spraying, spraying followed by dipping, brushing, orroll-coating. In certain embodiments, the solution or dispersion whenapplied to the metal substrate is at a temperature ranging from 60 to150° F. (15 to 65° C.). The contact time is often from 10 seconds tofive minutes, such as 30 seconds to 2 minutes.

As used herein, the term “group IIIB and/or IVB metal” refers to anelement that is in group IIIB or group IVB of the CAS Periodic Table ofthe Elements as is shown, for example, in the Handbook of Chemistry andPhysics, 63^(rd) edition (1983). Where applicable, the metal themselvesmay be used. In certain embodiments, a group IIIB and/or IVB metalcompound is used. As used herein, the term “group IIIB and/or IVB metalcompound” refers to compounds that include at least one element that isin group IIIB or group IVB of the CAS Periodic Table of the Elements.

In certain embodiments, the group IIIB and/or IVB metal compound used inthe pretreatment composition is a compound of zirconium, titanium,hafnium, yttrium, cerium, or a mixture thereof. Suitable compounds ofzirconium include, but are not limited to, hexafluorozirconic acid,alkali metal and ammonium salts thereof, ammonium zirconium carbonate,zirconyl nitrate, zirconium carboxylates and zirconium hydroxycarboxylates, such as hydrofluorozirconic acid, zirconium acetate,zirconium oxalate, ammonium zirconium glycolate, ammonium zirconiumlactate, ammonium zirconium citrate, and mixtures thereof. Suitablecompounds of titanium include, but are not limited to, fluorotitanicacid and its salts. A suitable compound of hafnium includes, but is notlimited to, hafnium nitrate. A suitable compound of yttrium includes,but is not limited to, yttrium nitrate. A suitable compound of ceriumincludes, but is not limited to, cerous nitrate.

In certain embodiments, the group TIM and/or IVB metal compound ispresent in the pretreatment composition in an amount of at least 10 ppmmetal, such as at least 100 ppm metal, or, in some cases, at least 150ppm metal. In certain embodiments, the group IIIB and/or IVB metalcompound is present in the pretreatment composition in an amount of nomore than 5000 ppm metal, such as no more than 300 ppm metal, or, insome cases, no more than 250 ppm metal. The amount of group IIIB and/orIVB metal in the pretreatment composition can range between anycombination of the recited values inclusive of the recited values. ThepH of the pretreatment composition often ranges from 2.0 to 7.0, such as3.5 to 5.5. The pH of the pretreatment composition may be adjustedusing, for example, any of the acids and bases identified earlier withrespect to cleaning the substrate.

In some embodiments, the pretreatment composition may be a silane or anon-crystalline phosphate, such as iron phosphate, containingpretreatment composition. Suitable silane containing pretreatmentcompositions include, but are not limited to, certain commerciallyavailable products, such as Silquest A-1100 Silane, which is describedin the Examples herein and which is commercially available fromMomentive Performance Materials. Suitable non-crystalline phosphatecontaining pretreatment composition include pretreatment compositionthat comprise, iron phosphate, manganese phosphate, calcium phosphate,magnesium phosphate, cobalt phosphate, or an organophosphate and/ororganophosphonate, such as is disclosed in U.S. Pat. No. 5,294,265 atcol. 1, line 53 to col. 3, line 12 and 5,306,526 at col. 1, line 46 tocol. 3, line 8, the cited portions of which being incorporated herein byreference. Suitable non-crystalline phosphate containing pretreatmentcompositions are commercially available, such as Chemfos® 158 andChemfos® 51, which are iron phosphate pretreatment compositionscommercially available from PPG Industries, Inc.

In certain embodiments, the pretreatment composition also comprises anelectropositive metal, such as copper. The source of electropositivemetal, such as copper, in the pretreatment composition may comprise, forexample, any of the materials described earlier with respect to theplating solution. In certain embodiments, the electropositive metal isincluded in such pretreatment compositions in an amount of at least 1ppm, such as at least 5 ppm, or in some cases, at least 10 ppm of totalmetal (measured as elemental metal). In certain embodiments, theelectropositive metal is included in such pretreatment compositions inan amount of no more than 500 ppm, such as no more than 100 ppm, or insome cases, no more than 50 ppm of total metal (measured as elementalmetal).

In certain embodiments, the pretreatment composition comprises aresinous binder. Suitable resins include reaction products of one ormore alkanolamines and an epoxy-functional material containing at leasttwo epoxy groups, such as those disclosed in U.S. Pat. No. 5,653,823. Insome cases, such resins contain beta hydroxy ester, imide, or sulfidefunctionality, incorporated by using dimethylolpropionic acid,phthalimide, or mercapto glycerine as an additional reactant in thepreparation of the resin. Alternatively, the reaction product is that ofthe diglycidyl ether of Bisphenol A (commercially available from ShellChemical Company as EPON 880), dimethylol propionic acid, anddiethanolamine in a 0.6 to 5.0:0.05 to 5.5:1 mole ratio. Other suitableresinous binders include water soluble and water dispersible polyacrylicacids as disclosed in U.S. Pat. Nos. 3,912,548 and 5,328,525; phenolformaldehyde resins as described in U.S. Pat. No. 5,662,746; watersoluble polyamides such as those disclosed in WO 95/33869; copolymers ofmaleic or acrylic acid with allyl ether as described in Canadian patentapplication 2,087,352; and water soluble and dispersible resinsincluding epoxy resins, aminoplasts, phenol-formaldehyde resins,tannins, and polyvinyl phenols as discussed in U.S. Pat. No. 5,449,415.

In these embodiments of the present invention, the resinous binder ispresent in the pretreatment composition in an amount of 0.005 percent to30 percent by weight, such as 0.5 to 3 percent by weight, based on thetotal weight of the ingredients in the composition.

In other embodiments, however, the pretreatment composition issubstantially free or, in some cases, completely free of any resinousbinder. As used herein, the term “substantially free”, when used withreference to the absence of resinous binder in the pretreatmentcomposition, means that any resinous binder is present in thepretreatment composition in an amount of less than 0.005 percent byweight. As used herein, the term “completely free” means that there isno resinous binder in the pretreatment composition at all.

The pretreatment composition may optionally contain other materials,such as nonionic surfactants and auxiliaries conventionally used in theart of pretreatment. In an aqueous medium, water dispersible organicsolvents, for example, alcohols with up to about 8 carbon atoms, such asmethanol, isopropanol, and the like, may be present; or glycol etherssuch as the monoalkyl ethers of ethylene glycol, diethylene glycol, orpropylene glycol, and the like. When present, water dispersible organicsolvents are typically used in amounts up to about ten percent byvolume, based on the total volume of aqueous medium.

Other optional materials include surfactants that function as defoamersor substrate wetting agents, such as those materials and amountsdescribed earlier with respect to the plating solution.

In certain embodiments, the pretreatment composition also comprises areaction accelerator, such as nitrite ions, nitro-group containingcompounds, hydroxylamine sulfate, persulfate ions, sulfite ions,hyposulfite ions, peroxides, iron (III) ions, citric acid ironcompounds, bromate ions, perchlorinate ions, chlorate ions, chloriteions as well as ascorbic acid, citric acid, tartaric acid, malonic acid,succinic acid and salts thereof. Specific examples of suitable materialsand their amounts are described in United States Patent ApplicationPublication No. 2004/0163736 A1 at [0032] to [0041], the cited portionof which being incorporated herein by reference.

In certain embodiments, the pretreatment composition also comprises afiller, such as a siliceous filler. Non-limiting examples of suitablefillers include silica, mica, montmorillonite, kaolinite, asbestos,talc, diatomaceous earth, vermiculite, natural and synthetic zeolites,cement, calcium silicate, aluminum silicate, sodium aluminum silicate,aluminum polysilicate, alumina silica gels, and glass particles. Inaddition to the siliceous fillers other finely divided particulatesubstantially water-insoluble fillers may also be employed. Examples ofsuch optional fillers include carbon black, charcoal, graphite, titaniumoxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia,magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate,strontium sulfate, calcium carbonate, and magnesium carbonate.

As indicated, in certain embodiments, the pretreatment composition issubstantially or, in some cases, completely free of chromate and/orheavy metal phosphate. As used herein, the term “substantially free”when used in reference to the absence of chromate and/or heavy metalphosphate, such as zinc phosphate, in the pretreatment composition meansthat these substances are not present in the composition to such anextent that they cause a burden on the environment. That is, they arenot substantially used and the formation of sludge, such as zincphosphate, formed in the case of using a treating agent based on zincphosphate, is eliminated.

Moreover, in certain embodiments, the pretreatment composition issubstantially free, or, in some cases, completely free of any organicmaterials. As used herein, the term “substantially free”, when used withreference to the absence of organic materials in the composition, meansthat any organic materials are present in the composition, if at all, asan incidental impurity. In other words, the presence of any organicmaterial does not affect the properties of the composition. As usedherein, the term “completely free” means that there is no organicmaterial in the composition at all.

In certain embodiments, the film coverage of the residue of thepretreatment coating composition generally ranges from 1 to 1000milligrams per square meter (mg/m²), such as 10 to 400 mg/m². Thethickness of the pretreatment coating can vary, but it is generally verythin, often having a thickness of less than 1 micrometer, in some casesit is from 1 to 500 nanometers, and, in yet other cases, it is 10 to 300nanometers.

In certain other embodiments of the present invention, the pretreatmentcomposition comprises (a) a rare earth metal; and (b) a zirconylcompound. These pretreatment compositions are applied directly to themetal substrate without the prior application of an electropositivemetal (i.e. in a one-step pretreatment process).

Often, the pretreatment composition comprises a carrier, often anaqueous medium, so that the composition is in the form of a solution ordispersion of the rare earth metal compound and/or other pretreatmentcomposition components in the carrier. In these embodiments, thesolution or dispersion may be brought into contact with the substrate byany of a variety of known techniques, such as dipping or immersion,spraying, intermittent spraying, dipping followed by spraying, sprayingfollowed by dipping, brushing, or roll-coating. In certain embodiments,the solution or dispersion when applied to the metal substrate is at atemperature ranging from 60 to 150° F. (15 to 65° C.). The contact timeis often from 10 seconds to five minutes, such as 30 seconds to 2minutes.

As defined by IUPAC and used herein, rare earth elements or rare earthmetals are a collection of seventeen chemical elements in the periodictable, specifically the fifteen lanthanoids (the fifteen elements withatomic numbers 57 through 71, from lanthanum to lutetium) plus scandiumand yttrium. Where applicable, the metal themselves may be used. Incertain embodiments, a rare earth metal compound is used. As usedherein, the term “rare earth metal compound” refers to compounds thatinclude at least one element that is a rare earth element as definedabove.

In certain embodiments, the rare earth metal compound used in thepretreatment composition is a compound of yttrium, cerium, praseodymium,or a mixture thereof. Exemplary compounds that may be used includepraseodymium chloride, praseodymium nitrate, praseodymium sulfate,cerium chloride, cerium nitrate, cerium sulfate, yttrium chloride,yttrium nitrate, yttrium sulfate.

In certain embodiments, the rare earth metal compound is present in thepretreatment composition in an amount of at least 10 ppm metal, such asat least 100 ppm metal, or, in some cases, at least 150 ppm metal. Incertain embodiments, the rare earth metal compound is present in thepretreatment composition in an amount of no more than 5000 ppm metal,such as no more than 300 ppm metal, or, in some cases, no more than 250ppm metal. The amount of rare earth metal in the pretreatmentcomposition can range between any of the recited values inclusive of therecited values.

As noted above, the pretreatment composition also comprises a zirconylcompound. A zirconyl compound, as defined herein, refers to a zirconiumcompound with an oxide or a hydroxide group on a zirconium atom.

In certain embodiments, the zirconyl compound in the pretreatmentcomposition is zirconyl nitrate (ZrO(NO₃)₂), zirconyl acetate, zirconylcarbonate, zirconyl sulfate, or a mixture thereof.

In certain embodiments, the ratio of zirconium (from the zirconylcompound or compounds) to rare earth metal (from the rare earth metal orrare earth metal compound) is between 200/1 and 1/1. In otherembodiments, the ratio is between 100/1 and 2/1. In certain embodiments,the ratio is 20/1.

In certain embodiments, the pretreatment composition also includes agroup IIIB, group IVB, and/or group VB metal. As used herein, the term“group IIIB, group IVB, and/or group VB metal” refers to an element thatis in group IIIB or group IVB or group VB of the CAS Periodic Table ofElements as is shown, for example, in the Handbook of Chemistry andPhysics, 63^(rd) edition (1983). Where applicable, the metal themselvesmay be used. In certain embodiments, a group IIIB, group IV and/or agroup VB metal compound is used. As used herein, the term “a group IIIB,group IV and/or a group VB metal compound” refers to compounds thatinclude at least one element that is in the group IIIB or group IVB orgroup VB of the CAS Periodic Table of Elements.

In certain embodiments, the group IIIB or group IVB or group VB metalcompound used in the pretreatment composition is a compound ofzirconium, titanium, hafnium, yttrium, cerium, praseodymium, or amixture thereof. Suitable compounds of zirconium include, but are notlimited to, hexafluorozirconic acid, alkali metal and ammonium saltsthereof, ammonium zirconium carbonate, zirconyl nitrate, zirconiumcarboxylates and zirconium hydroxy carboxylates, such ashydrofluorozirconic acid, zirconium acetate, zirconium oxalate, ammoniumzirconium glycolate, ammonium zirconium lactate, ammonium zirconiumcitrate, and mixtures thereof. Suitable compounds of titanium include,but are not limited to, fluorotitanic acid and its salts. A suitablecompound of hafnium includes, but is not limited to, hafnium nitrate. Asuitable compound of yttrium includes, but is not limited to, yttriumnitrate. A suitable compound of cerium includes, but is not limited to,cerous nitrate.

In certain embodiments, the group IIIB or group IVB or group VB metalcompound is present in the pretreatment composition in an amount of atleast 10 ppm metal, such as at least 100 ppm metal, or, in some cases,at least 150 ppm metal. In certain embodiments, the group IIIB or groupIVB or group VB metal compound is present in the pretreatmentcomposition in an amount of no more than 5000 ppm metal, such as no morethan 300 ppm metal, or, in some cases, no more than 250 ppm metal. Theamount of group IIIB or group IVB or group VB metal in the pretreatmentcomposition can range between any combination of the recited valuesinclusive of the recited values.

In certain embodiments, the pretreatment composition also comprises anelectropositive metal. As used herein, the term “electropositive metal”refers to metals that are more electropositive than the metal substrate.This means that, for purposes of the present invention, the term“electropositive metal” encompasses metals that are less easily oxidizedthan the metal of the metal substrate. As will be appreciated by thoseskilled in the art, the tendency of a metal to be oxidized is called theoxidation potential, is expressed in volts, and is measured relative toa standard hydrogen electrode, which is arbitrarily assigned anoxidation potential of zero. The oxidation potential for severalelements is set forth in the table below. An element is less easilyoxidized than another element if it has a voltage value, E*, in thefollowing table, that is greater than the element to which it is beingcompared.

Element Half-cell reaction Voltage, E* Potassium K⁺ + e → K −2.93Calcium Ca²⁺ + 2e → Ca −2.87 Sodium Na⁺ + e → Na −2.71 Magnesium Mg²⁺ +2e → Mg −2.37 Aluminum Al³⁺ + 3e → Al −1.66 Zinc Zn²⁺ + 2e → Zn −0.76Iron Fe²⁺ + 2e → Fe −0.44 Nickel Ni²⁺ + 2e → Ni −0.25 Tin Sn²⁺ + 2e → Sn−0.14 Lead Pb²⁺ + 2e → Pb −0.13 Hydrogen 2H⁺ + 2e → H₂ −0.00 CopperCu²⁺ + 2e → Cu 0.34 Mercury Hg₂ ²⁺ + 2e → 2Hg 0.79 Silver Ag⁺ + e → Ag0.80 Gold Au³⁺ + 3e → Au 1.50

Thus, as will be apparent, when the metal substrate comprises one of thematerials listed earlier, such as cold rolled steel, hot rolled steel,steel coated with zinc metal, zinc compounds, or zinc alloys, hot-dippedgalvanized steel, galvanealed steel, steel plated with zinc alloy,aluminum alloys, aluminum plated steel, aluminum alloy plated steel,magnesium and magnesium alloys, suitable electropositive metals fordeposition thereon in accordance with the present invention include, forexample, nickel, copper, silver, and gold, as well mixtures thereof.

In certain embodiments, the source of electropositive metal in thepretreatment composition is a water soluble metal salt. In certainembodiments of the present invention, the water soluble metal salt is awater soluble copper compound. Specific examples of water soluble coppercompounds, which are suitable for use in the present invention include,but are not limited to, copper cyanide, copper potassium cyanide, coppersulfate, copper nitrate, copper pyrophosphate, copper thiocyanate,disodium copper ethylenediaminetetraacetate tetrahydrate, copperbromide, copper oxide, copper hydroxide, copper chloride, copperfluoride, copper gluconate, copper citrate, copper lauroyl sarcosinate,copper formate, copper acetate, copper propionate, copper butyrate,copper lactate, copper oxalate, copper phytate, copper tartarate, coppermalate, copper succinate, copper malonate, copper maleate, copperbenzoate, copper salicylate, copper aspartate, copper glutamate, copperfumarate, copper glycerophosphate, sodium copper chlorophyllin, copperfluorosilicate, copper fluoroborate and copper iodate, as well as coppersalts of carboxylic acids in the homologous series formic acid todecanoic acid, copper salts of polybasic acids in the series oxalic acidto suberic acid, and copper salts of hydroxycarboxylic acids, includingglycolic, lactic, tartaric, malic and citric acids.

When copper ions supplied from such a water-soluble copper compound areprecipitated as an impurity in the form of copper sulfate, copper oxide,etc., it may be preferable to add a complexing agent that suppresses theprecipitation of copper ions, thus stabilizing them as a copper complexin the solution.

In certain embodiments, the copper compound is added as a copper complexsalt such as K₃Cu(CN)₄ or Cu-EDTA, which can be present stably in thecomposition on its own, but it is also possible to form a copper complexthat can be present stably in the composition by combining a complexingagent with a compound that is difficultly soluble on its own. Examplesthereof include a copper cyanide complex formed by a combination of CuCNand KCN or a combination of CuSCN and KSCN or KCN, and a Cu-EDTA complexformed by a combination of CuSO₄ and EDTA.2Na.

With regard to the complexing agent, a compound that can form a complexwith copper ions can be used; examples thereof include inorganiccompounds, such as cyanide compounds and thiocyanate compounds, andpolycarboxylic acids, and specific examples thereof includeethylenediaminetetraacetic acid, salts of ethylenediaminetetraaceticacid, such as dihydrogen disodium ethylenediaminetetraacetate dihydrate,aminocarboxylic acids, such as nitrilotriacetic acid and iminodiaceticacid, oxycarboxylic acids, such as citric acid and tartaric acid,succinic acid, oxalic acid, ethylenediaminetetramethylenephosphonicacid, and glycine.

In certain embodiments, the electropositive metal, such as copper, isincluded in the pretreatment compositions in an amount of at least 1ppm, such as at least 5 ppm, or in some cases, at least 10 ppm of totalmetal (measured as elemental metal). In certain embodiments, theelectropositive metal is included in such pretreatment compositions inan amount of no more than 500 ppm, such as no more than 100 ppm, or insome cases, no more than 50 ppm of total metal (measured as elementalmetal). The amount of electropositive metal in the pretreatmentcomposition can range between any combination of the recited valuesinclusive of the recited values.

The pretreatment composition may optionally contain other materials,such as nonionic surfactants and auxiliaries conventionally used in theart of pretreatment. In an aqueous medium, water dispersible organicsolvents, for example, alcohols with up to about 8 carbon atoms, such asmethanol, isopropanol, and the like, may be present; or glycol etherssuch as the monoalkyl ethers of ethylene glycol, diethylene glycol, orpropylene glycol, and the like. When present, water dispersible organicsolvents are typically used in amounts up to about ten percent byvolume, based on the total volume of aqueous medium.

Other optional materials include surfactants that function as defoamersor substrate wetting agents, such as those materials and amountsdescribed earlier with respect to the plating solution.

In certain embodiments, the pretreatment composition also comprises areaction accelerator, such as nitrite ions, nitro-group containingcompounds, hydroxylamine sulfate, persulfate ions, sulfite ions,hyposulfite ions, peroxides, iron (III) ions, citric acid ironcompounds, bromate ions, perchlorinate ions, chlorate ions, chloriteions as well as ascorbic acid, citric acid, tartaric acid, malonic acid,succinic acid and salts thereof. Specific examples of suitable materialsand their amounts are described in United States Patent ApplicationPublication No. 2004/0163736 A1 at [0032] to [0041], the cited portionof which being incorporated herein by reference.

In certain embodiments, the pretreatment composition also comprises afiller, such as a siliceous filler. Non-limiting examples of suitablefillers include silica, mica, montmorillonite, kaolinite, asbestos,talc, diatomaceous earth, vermiculite, natural and synthetic zeolites,cement, calcium silicate, aluminum silicate, sodium aluminum silicate,aluminum polysilicate, alumina silica gels, and glass particles. Inaddition to the siliceous fillers other finely divided particulatesubstantially water-insoluble fillers may also be employed. Examples ofsuch optional fillers include carbon black, charcoal, graphite, titaniumoxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia,magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate,strontium sulfate, calcium carbonate, and magnesium carbonate.

As indicated, in certain embodiments, the pretreatment composition issubstantially or, in some cases, completely free of chromate and/orheavy metal phosphate. As used herein, the term “substantially free”when used in reference to the absence of chromate and/or heavy metalphosphate, such as zinc phosphate, in the pretreatment composition meansthat these substances are not present in the composition to such anextent that they cause a burden on the environment. That is, they arenot substantially used and the formation of sludge, such as zincphosphate, formed in the case of using a treating agent based on zincphosphate, is eliminated.

Moreover, in certain embodiments, the pretreatment composition issubstantially free, or, in some cases, completely free of any organicmaterials. As used herein, the term “substantially free”, when used withreference to the absence of organic materials in the composition, meansthat any organic materials are present in the composition, if at all, asan incidental impurity. In other words, the presence of any organicmaterial does not affect the properties of the composition. As usedherein, the term “completely free” means that there is no organicmaterial in the composition at all.

In certain embodiments, the film coverage of the residue of thepretreatment coating composition generally ranges from 1 to 1000milligrams per square meter (mg/m²), such as 10 to 400 mg/m². Thethickness of the pretreatment coating can vary, but it is generally verythin, often having a thickness of less than 1 micrometer, in some casesit is from 1 to 500 nanometers, and, in yet other cases, it is 10 to 300nanometers.

Following contact with the pretreatment solution according to any of theabove embodiments, the substrate may be rinsed with water and dried.

Additional Coating Composition or Compositions after Pretreatment

In certain embodiments of the methods of the present invention, afterthe substrate is contacted with the acid and optional alkaline cleanerand optionally with a pretreatment composition, it is then contactedwith a coating composition comprising a film-forming resin. Any suitabletechnique may be used to contact the substrate with such a coatingcomposition, including, for example, brushing, dipping, flow coating,spraying and the like. In certain embodiments, however, as described inmore detail below, such contacting comprises an electrocoating stepwherein an electrodepositable composition is deposited onto the metalsubstrate by electrodeposition.

As used herein, the term “film-forming resin” refers to resins that canform a self-supporting continuous film on at least a horizontal surfaceof a substrate upon removal of any diluents or carriers present in thecomposition or upon curing at ambient or elevated temperature.Conventional film-forming resins that may be used include, withoutlimitation, those typically used in automotive OEM coating compositions,automotive refinish coating compositions, industrial coatingcompositions, architectural coating compositions, coil coatingcompositions, and aerospace coating compositions, among others.

In certain embodiments, the coating composition comprises athermosetting film-forming resin. As used herein, the term“thermosetting” refers to resins that “set” irreversibly upon curing orcrosslinking, wherein the polymer chains of the polymeric components arejoined together by covalent bonds. This property is usually associatedwith a cross-linking reaction of the composition constituents ofteninduced, for example, by heat or radiation. Curing or crosslinkingreactions also may be carried out under ambient conditions. Once curedor crosslinked, a thermosetting resin will not melt upon the applicationof heat and is insoluble in solvents. In other embodiments, the coatingcomposition comprises a thermoplastic film-forming resin. As usedherein, the term “thermoplastic” refers to resins that comprisepolymeric components that are not joined by covalent bonds and therebycan undergo liquid flow upon heating and are soluble in solvents.

As previously indicated, in certain embodiments, the substrate iscontacted with a coating composition comprising a film-forming resin byan electrocoating step wherein an electrodepositable composition isdeposited onto the metal substrate by electrodeposition. In the processof electrodeposition, the metal substrate being treated, serving as anelectrode, and an electrically conductive counter electrode are placedin contact with an ionic, electrodepositable composition. Upon passageof an electric current between the electrode and counter electrode whilethey are in contact with the electrodepositable composition, an adherentfilm of the electrodepositable composition will deposit in asubstantially continuous manner on the metal substrate.

Electrodeposition is usually carried out at a constant voltage in therange of from 1 volt to several thousand volts, typically between 50 and500 volts. Current density is usually between 1.0 ampere and 15 amperesper square foot (10.8 to 161.5 amperes per square meter) and tends todecrease quickly during the electrodeposition process, indicatingformation of a continuous self-insulating film.

The electrodepositable composition utilized in certain embodiments ofthe present invention often comprises a resinous phase dispersed in anaqueous medium wherein the resinous phase comprises: (a) an activehydrogen group-containing ionic electrodepositable resin, and (b) acuring agent having functional groups reactive with the active hydrogengroups of (a).

In certain embodiments, the electrodepositable compositions utilized incertain embodiments of the present invention contain, as a mainfilm-forming polymer, an active hydrogen-containing ionic, oftencationic, electrodepositable resin. A wide variety of electrodepositablefilm-forming resins are known and can be used in the present inventionso long as the polymers are “water dispersible,” i.e., adapted to besolubilized, dispersed or emulsified in water. The water dispersiblepolymer is ionic in nature, that is, the polymer will contain anionicfunctional groups to impart a negative charge or, as is often preferred,cationic functional groups to impart a positive charge.

Examples of film-forming resins suitable for use in anionicelectrodepositable compositions are base-solubilized, carboxylic acidcontaining polymers, such as the reaction product or adduct of a dryingoil or semi-drying fatty acid ester with a dicarboxylic acid oranhydride; and the reaction product of a fatty acid ester, unsaturatedacid or anhydride and any additional unsaturated modifying materialswhich are further reacted with polyol. Also suitable are the at leastpartially neutralized interpolymers of hydroxy-alkyl esters ofunsaturated carboxylic acids, unsaturated carboxylic acid and at leastone other ethylenically unsaturated monomer. Still another suitableelectrodepositable film-forming resin comprises an alkyd-aminoplastvehicle, i.e., a vehicle containing an alkyd resin and an amine-aldehyderesin. Yet another anionic electrodepositable resin compositioncomprises mixed esters of a resinous polyol, such as is described inU.S. Pat. No. 3,749,657 at col. 9, lines 1 to 75 and col. 10, lines 1 to13, the cited portion of which being incorporated herein by reference.Other acid functional polymers can also be used, such as phosphatizedpolyepoxide or phosphatized acrylic polymers as are known to thoseskilled in the art.

As aforementioned, it is often desirable that the activehydrogen-containing ionic electrodepositable resin (a) is cationic andcapable of deposition on a cathode. Examples of such cationicfilm-forming resins include amine salt group-containing resins, such asthe acid-solubilized reaction products of polyepoxides and primary orsecondary amines, such as those described in U.S. Pat. Nos. 3,663,389;3,984,299; 3,947,338; and 3,947,339. Often, these amine saltgroup-containing resins are used in combination with a blockedisocyanate curing agent. The isocyanate can be fully blocked, asdescribed in U.S. Pat. No. 3,984,299, or the isocyanate can be partiallyblocked and reacted with the resin backbone, such as is described inU.S. Pat. No. 3,947,338. Also, one-component compositions as describedin U.S. Pat. No. 4,134,866 and DE-OS No. 2,707,405 can be used as thefilm-forming resin. Besides the epoxy-amine reaction products,film-forming resins can also be selected from cationic acrylic resins,such as those described in U.S. Pat. Nos. 3,455,806 and 3,928,157.

Besides amine salt group-containing resins, quaternary ammonium saltgroup-containing resins can also be employed, such as those formed fromreacting an organic polyepoxide with a tertiary amine salt as describedin U.S. Pat. Nos. 3,962,165; 3,975,346; and 4,001,101. Examples of othercationic resins are ternary sulfonium salt group-containing resins andquaternary phosphonium salt-group containing resins, such as thosedescribed in U.S. Pat. Nos. 3,793,278 and 3,984,922, respectively. Also,film-forming resins which cure via transesterification, such asdescribed in European Application No. 12463 can be used. Further,cationic compositions prepared from Mannich bases, such as described inU.S. Pat. No. 4,134,932, can be used.

In certain embodiments, the resins present in the electrodepositablecomposition are positively charged resins which contain primary and/orsecondary amine groups, such as described in U.S. Pat. Nos. 3,663,389;3,947,339; and 4,116,900. In U.S. Pat. No. 3,947,339, a polyketiminederivative of a polyamine, such as diethylenetriamine ortriethylenetetraamine, is reacted with a polyepoxide. When the reactionproduct is neutralized with acid and dispersed in water, free primaryamine groups are generated. Also, equivalent products are formed whenpolyepoxide is reacted with excess polyamines, such asdiethylenetriamine and triethylenetetraamine, and the excess polyaminevacuum stripped from the reaction mixture, as described in U.S. Pat.Nos. 3,663,389 and 4,116,900.

In certain embodiments, the active hydrogen-containing ionicelectrodepositable resin is present in the electrodepositablecomposition in an amount of 1 to 60 percent by weight, such as 5 to 25percent by weight, based on total weight of the electrodeposition bath.

As indicated, the resinous phase of the electrodepositable compositionoften further comprises a curing agent adapted to react with the activehydrogen groups of the ionic electrodepositable resin. For example, bothblocked organic polyisocyanate and aminoplast curing agents are suitablefor use in the present invention, although blocked isocyanates are oftenpreferred for cathodic electrodeposition.

Aminoplast resins, which are often the preferred curing agent foranionic electrodeposition, are the condensation products of amines oramides with aldehydes. Examples of suitable amine or amides aremelamine, benzoguanamine, urea and similar compounds. Generally, thealdehyde employed is formaldehyde, although products can be made fromother aldehydes, such as acetaldehyde and furfural. The condensationproducts contain methylol groups or similar alkylol groups depending onthe particular aldehyde employed. Often, these methylol groups areetherified by reaction with an alcohol, such as a monohydric alcoholcontaining from 1 to 4 carbon atoms, such as methanol, ethanol,isopropanol, and n-butanol. Aminoplast resins are commercially availablefrom American Cyanamid Co. under the trademark CYMEL and from MonsantoChemical Co. under the trademark RESIMENE.

The aminoplast curing agents are often utilized in conjunction with theactive hydrogen containing anionic electrodepositable resin in amountsranging from 5 percent to 60 percent by weight, such as from 20 percentto 40 percent by weight, the percentages based on the total weight ofthe resin solids in the electrodepositable composition.

As indicated, blocked organic polyisocyanates are often used as thecuring agent in cathodic electrodeposition compositions. Thepolyisocyanates can be fully blocked as described in U.S. Pat. No.3,984,299 at col. 1, lines 1 to 68, col. 2, and col. 3, lines 1 to 15,or partially blocked and reacted with the polymer backbone as describedin U.S. Pat. No. 3,947,338 at col. 2, lines 65 to 68, col. 3, and col. 4lines 1 to 30, the cited portions of which being incorporated herein byreference. By “blocked” is meant that the isocyanate groups have beenreacted with a compound so that the resultant blocked isocyanate groupis stable to active hydrogens at ambient temperature but reactive withactive hydrogens in the film forming polymer at elevated temperaturesusually between 90° C. and 200° C.

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates,including cycloaliphatic polyisocyanates and representative examplesinclude diphenylmethane-4,4′-diisocyanate (MDI), 2,4- or 2,6-toluenediisocyanate (TDI), including mixtures thereof, p-phenylenediisocyanate, tetramethylene and hexamethylene diisocyanates,dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, mixturesof phenylmethane-4,4′-diisocyanate and polymethylenepolyphenylisocyanate. Higher polyisocyanates, such as triisocyanates canbe used. An example would includetriphenylmethane-4,4′,4″-triisocyanate. Isocyanate ( )-prepolymers withpolyols such as neopentyl glycol and trimethylolpropane and withpolymeric polyols such as polycaprolactone diols and triols (NCO/OHequivalent ratio greater than 1) can also be used.

The polyisocyanate curing agents are typically utilized in conjunctionwith the active hydrogen containing cationic electrodepositable resin inamounts ranging from 5 percent to 60 percent by weight, such as from 20percent to 50 percent by weight, the percentages based on the totalweight of the resin solids of the electrodepositable composition.

In certain embodiments, the coating composition comprising afilm-forming resin also comprises yttrium. In certain embodiments,yttrium is present in such compositions in an amount from 10 to 10,000ppm, such as not more than 5,000 ppm, and, in some cases, not more than1,000 ppm, of total yttrium (measured as elemental yttrium).

Both soluble and insoluble yttrium compounds may serve as the source ofyttrium. Examples of yttrium sources suitable for use in lead-freeelectrodepositable coating compositions are soluble organic andinorganic yttrium salts such as yttrium acetate, yttrium chloride,yttrium formate, yttrium carbonate, yttrium sulfamate, yttrium lactateand yttrium nitrate. When the yttrium is to be added to an electrocoatbath as an aqueous solution, yttrium nitrate, a readily availableyttrium compound, is a preferred yttrium source. Other yttrium compoundssuitable for use in electrodepositable compositions are organic andinorganic yttrium compounds such as yttrium oxide, yttrium bromide,yttrium hydroxide, yttrium molybdate, yttrium sulfate, yttrium silicate,and yttrium oxalate. Organoyttrium complexes and yttrium metal can alsobe used. When the yttrium is to be incorporated into an electrocoat bathas a component in the pigment paste, yttrium oxide is often thepreferred source of yttrium.

The electrodepositable compositions described herein are in the form ofan aqueous dispersion. The term “dispersion” is believed to be atwo-phase transparent, translucent or opaque resinous system in whichthe resin is in the dispersed phase and the water is in the continuousphase. The average particle size of the resinous phase is generally lessthan 1.0 and usually less than 0.5 microns, often less than 0.15 micron.

The concentration of the resinous phase in the aqueous medium is oftenat least 1 percent by weight, such as from 2 to 60 percent by weight,based on total weight of the aqueous dispersion. When such compositionsare in the form of resin concentrates, they generally have a resinsolids content of 20 to 60 percent by weight based on weight of theaqueous dispersion.

The electrodepositable compositions described herein are often suppliedas two components: (1) a clear resin feed, which includes generally theactive hydrogen-containing ionic electrodepositable resin, i.e., themain film-forming polymer, the curing agent, and any additionalwater-dispersible, non-pigmented components; and (2) a pigment paste,which generally includes one or more colorants (described below), awater-dispersible grind resin which can be the same or different fromthe main-film forming polymer, and, optionally, additives such aswetting or dispersing aids. Electrodeposition bath components (1) and(2) are dispersed in an aqueous medium which comprises water and,usually, coalescing solvents.

As aforementioned, besides water, the aqueous medium may contain acoalescing solvent. Useful coalescing solvents are often hydrocarbons,alcohols, esters, ethers and ketones. The preferred coalescing solventsare often alcohols, polyols and ketones. Specific coalescing solventsinclude isopropanol, butanol, 2-ethylhexanol, isophorone,2-methoxypentanone, ethylene and propylene glycol and the monoethylmonobutyl and monohexyl ethers of ethylene glycol. The amount ofcoalescing solvent is generally between 0.01 and 25 percent, such asfrom 0.05 to 5 percent by weight based on total weight of the aqueousmedium.

In addition, a colorant and, if desired, various additives such assurfactants, wetting agents or catalyst can be included in the coatingcomposition comprising a film-forming resin. As used herein, the term“colorant” means any substance that imparts color and/or other opacityand/or other visual effect to the composition. The colorant can be addedto the composition in any suitable form, such as discrete particles,dispersions, solutions and/or flakes. A single colorant or a mixture oftwo or more colorants can be used.

Example colorants include pigments, dyes and tints, such as those usedin the paint industry and/or listed in the Dry Color ManufacturersAssociation (DCMA), as well as special effect compositions. A colorantmay include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant can beorganic or inorganic and can be agglomerated or non-agglomerated.Colorants can be incorporated by use of a grind vehicle, such as anacrylic grind vehicle, the use of which will be familiar to one skilledin the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, disazo,naphthol AS, salt type (lakes), benzimidazolone, condensation, metalcomplex, isoindolinone, isoindoline and polycyclic phthalocyanine,quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo,anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments,diketo pyrrolo pyrrole red (“DPPBO red”), titanium dioxide, carbon blackand mixtures thereof. The terms “pigment” and “colored filler” can beused interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, perylene, aluminum and quinacridone.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5min. Example nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800 B2, which is incorporated hereinby reference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution). In order to minimizere-agglomeration of nanoparticles within the coating, a dispersion ofresin-coated nanoparticles can be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in which isdispersed discreet “composite microparticles” that comprise ananoparticle and a resin coating on the nanoparticle. Exampledispersions of resin-coated nanoparticles and methods for making themare identified in United States Patent Application Publication2005-0287348 A1, filed Jun. 24, 2004, U.S. Provisional Application No.60/482,167 filed Jun. 24, 2003, and U.S. patent application Ser. No.11/337,062, filed Jan. 20, 2006, which is also incorporated herein byreference.

Example special effect compositions that may be used include pigmentsand/or compositions that produce one or more appearance effects such asreflectance, pearlescence, metallic sheen, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism and/or color-change. Additional special effectcompositions can provide other perceptible properties, such as opacityor texture. In certain embodiments, special effect compositions canproduce a color shift, such that the color of the coating changes whenthe coating is viewed at different angles. Example color effectcompositions are identified in U.S. Pat. No. 6,894,086, incorporatedherein by reference. Additional color effect compositions can includetransparent coated mica and/or synthetic mica, coated silica, coatedalumina, a transparent liquid crystal pigment, a liquid crystal coating,and/or any composition wherein interference results from a refractiveindex differential within the material and not because of the refractiveindex differential between the surface of the material and the air.

In certain embodiments, a photosensitive composition and/or photochromiccomposition, which reversibly alters its color when exposed to one ormore light sources, can be used. Photochromic and/or photosensitivecompositions can be activated by exposure to radiation of a specifiedwavelength. When the composition becomes excited, the molecularstructure is changed and the altered structure exhibits a new color thatis different from the original color of the composition. When theexposure to radiation is removed, the photochromic and/or photosensitivecomposition can return to a state of rest, in which the original colorof the composition returns. In certain embodiments, the photochromicand/or photosensitive composition can be colorless in a non-excitedstate and exhibit a color in an excited state. Full color-change canappear within milliseconds to several minutes, such as from 20 secondsto 60 seconds. Example photochromic and/or photosensitive compositionsinclude photochromic dyes.

In certain embodiments, the photosensitive composition and/orphotochromic composition can be associated with and/or at leastpartially bound to, such as by covalent bonding, a polymer and/orpolymeric materials of a polymerizable component. In contrast to somecoatings in which the photosensitive composition may migrate out of thecoating and crystallize into the substrate, the photosensitivecomposition and/or photochromic composition associated with and/or atleast partially bound to a polymer and/or polymerizable component inaccordance with certain embodiments of the present invention, haveminimal migration out of the coating. Example photosensitivecompositions and/or photochromic compositions and methods for makingthem are identified in U.S. application Ser. No. 10/892,919 filed Jul.16, 2004, incorporated herein by reference.

In general, the colorant can be present in the coating composition inany amount sufficient to impart the desired visual and/or color effect.The colorant may comprise from 1 to 65 weight percent, such as from 3 to40 weight percent or 5 to 35 weight percent, with weight percent basedon the total weight of the composition.

After deposition, the coating is often heated to cure the depositedcomposition. The heating or curing operation is often carried out at atemperature in the range of from 120 to 250° C., such as from 120 to190° C., for a period of time ranging from 10 to 60 minutes. In certainembodiments, the thickness of the resultant film is from 10 to 50microns.

Electrodepositable Coating Composition without Pretreatment

In certain embodiments of the methods of the present invention, afterthe substrate is contacted with the acid and without the subsequentcontact with a pretreatment composition, it may then be contacted with aelectrodepositable coating composition comprising (i) a film-formingcompound and (ii) a source of yttrium.

As defined herein, the term “without the subsequent contact with apretreatment composition” means that the substrate has not beencontacted with a composition that, upon contact with the substrate,reacts with and chemically alters the substrate surface and binds to itto form a protective layer. This specifically includes any of thepretreatment compositions comprising a group IIIB and/or group IVB metalas described above, and further includes other known pretreatmentcompositions such as, for example, zinc or iron phosphate-typeconversion or pretreatment coatings.

In certain embodiments, the electrodepositable coating composition maybe formed in accordance with U.S. patent application Ser. No.12/693,626, which is herein incorporated by reference, and may alsoinclude (iii) a silane that does not contain an ethylenicallyunsaturated double bond. In certain embodiments, the coating compositionmay be formed in accordance with U.S. patent application Ser. No.12/693,626 and may further also include (iii) an aminosilane, whichcould or could not contain an ethylenically unsaturated double bond.

In some embodiments, when the film-forming polymer comprises a reactivefunctional group, the coating composition further comprises (iv) acuring agent that is reactive with a reactive functional group of thefilm-forming polymer.

A wide variety of film-forming polymers, which are known in the art, canbe used as component (i) so long as the polymers are “waterdispersible.” As used herein, “water dispersible” means that a materialis adapted to be solubilized, dispersed, and/or emulsified in water. Thefilm-forming polymers used in the present invention are ionic in nature.Accordingly, in some embodiments, the film-forming polymer is cationic.In other words, the film-forming polymer comprises cationic salt groups,generally prepared by neutralizing a functional group on thefilm-forming polymer with an acid, which enables the film-formingpolymer to be electrodeposited onto a cathode.

Examples of film-forming polymers suitable for use in cationicelectrocoating coating compositions include, without limitation,cationic polymers derived from a polyepoxide, an acrylic, apolyurethane, and/or polyester. In certain embodiments, the film-formingpolymer comprises reactive functional groups. As used herein, the phrase“reactive functional group” means hydroxyl, carboxyl, carbamate, epoxy,isocyanate, aceto acetate, amine-salt, mercaptan, or combinationsthereof. It should be noted that in some embodiments, the film-formingpolymer is a copolymer of the polymers listed in the preceding sentence.In some embodiments, the cationic polymer can be derived by reacting apolyepoxide containing polymer with a cationic salt group former. Asused herein, “cationic salt group former” means a material that isreactive with epoxy groups and which can be acidified before, during, orafter reaction with the epoxy groups to form cationic salt groups.Suitable materials that can be used as the cationic salt group formerinclude amines such as primary or secondary amines, which can beacidified after reaction with the epoxy groups to form amine saltgroups, or tertiary amines, which can be acidified prior to reactionwith the epoxy groups and which after reaction with the epoxy groupsform quaternary ammonium salt groups. Examples of other cationic saltgroup formers are sulfides which can be mixed with acid prior toreaction with the epoxy groups and form ternary sulfonium salt groupsupon subsequent reaction with the epoxy groups.

In certain embodiments, the film-forming polymer (i) that is used in thepresent invention comprises the reaction product of an epoxy functionalcompound (e.g., EPON 880) and a phenolic hydroxyl group-containingmaterial such as bisphenol A, which is a polyhydric phenol. In someembodiments, the film-forming polymer (i) described in the precedingsentence can be reacted with an amine, such as aminopropyldiethanolamine(APDEA) and dimethylaminopropylamine (DMAPA), in order to make thefilm-forming polymer water dispersible. In certain embodiments, ketiminecan be reacted with the backbone of the film-forming polymer therebyforming ketimine arms that extend pendant to the backbone. When thepolymer is dispersed in a water/acid mixture, the ketimine arms willhydrolyze and form primary amines. Accordingly, in some embodiments, theelectrodepositable coating compositions that are disclosed in U.S. Pat.Nos. 5,633,297, 5,820,987, and/or 5,936,012 can be used with the presentinvention.

Various corrosion inhibitors may be used as component (a) in the presentinvention. Suitable corrosion inhibitors include, without limitation,rare earth metals, bismuth, copper, zinc, silver, zirconium, orcombinations thereof. In certain embodiments, an yttrium compound or acerium compound, or a mixture of an yttrium and cerium compound, may beused as the corrosion inhibitor. Yttrium and cerium compounds, asdefined herein, include their respective salts and hereinafter may bereferred to simply as yttrium compounds or cerium compounds. They mayalso be included in the list of potential compounds comprising a sourceor yttrium or a source of cerium.

Various yttrium compounds may be used as component (ii) in the presentinvention. For example, the yttrium compounds may include, withoutlimitation, yttrium formate, yttrium acetate, yttrium lactate, yttriumsulfamate, yttrium methane sulfonate, yttrium nitrate, or combinationsthereof. In some embodiments, yttrium comprises ≦5 weight % of the totalresin solids of the electrodepositable coating composition. In otherembodiments, yttrium comprises ≧0.15 weight % of the total resin solidsof the electrodepositable coating composition. In certain embodiments,the amount of yttrium can range between any combination of values, whichwere recited in the preceding sentences, inclusive of the recitedvalues. For example, in certain embodiments, the amount of yttrium canrange from 0.20 weight % to 2 weight % of the total resin solids of theelectrodepositable coating composition.

Various cerium compounds may be used as component (ii) in the presentinvention. For example, the cerium compounds may include ammonium ceriumnitrate, ammonium cerium sulfate, cerium acetate, cerium bromide, ceriumcarbonate, cerium chloride, cerium fluoride, cerium iodide, ceriumnitrate, cerium molybdate, cerium oxide, cerium oxalate, ceriumphosphate, and cerium sulfate. In some embodiments, cerium comprises ≦5weight % of the total resin solids of the electrodepositable coatingcomposition. In other embodiments, cerium comprises ≧0.15 weight % ofthe total resin solids of the electrodepositable coating composition. Incertain embodiments, the amount of cerium can range between anycombination of values, which were recited in the preceding sentences,inclusive of the recited values. For example, in certain embodiments,the amount of cerium can range from 0.20 weight % to 2 weight % of thetotal resin solids of the electrodepositable coating composition.

Various combinations of yttrium compounds and cerium compounds, asdescribed in the previous paragraphs, may be used as component (ii) inthe present invention. In some embodiments, the combination of yttriumand cerium comprises ≦5 weight % of the total resin solids of theelectrodepositable coating composition. In other embodiments, thecombination of yttrium and cerium comprises ≧0.15 weight % of the totalresin solids of the electrodepositable coating composition. In certainembodiments, the amount of yttrium and cerium can range between anycombination of values, which were recited in the preceding sentences,inclusive of the recited values. For example, in certain embodiments,the amount of yttrium and cerium can range from 0.20 weight % to 2weight % of the total resin solids of the electrodepositable coatingcomposition.

If (i) the film-forming polymer comprises reactive functional groups,such as those described above, then the electrodepositable coatingcomposition may further comprise (iv) a crosslinking agent (“curingagent”) that is reactive with the reactive functional groups of thepolymer. Suitable crosslinking agents include, without limitation,aminoplasts, polyisocyanates (including blocked isocyanates),polyepoxides, beta-hydroxyalkylamides, polyacids, anhydrides,organometallic acid-functional materials, polyamines, polyamides, cycliccarbonates, siloxanes, or combinations thereof. In some embodiments, thecuring agent can comprise from 30 weight % to 40 weight % of the totalresin solids of the coating composition.

In certain embodiments, the electrodepositable coating composition mayfurther comprise (v) a curing catalyst, which may be used to catalyzethe reaction between the crosslinking agent and the reactive functionalgroups of the film-forming polymer. Suitable curing catalysts that maybe used as component (v) include, without limitation, organotincompounds (e.g., dibutyltin oxide, dioctyltin oxide) and salts thereof(e.g., dibutyltin diacetate); other metal oxides (e.g., oxides ofcerium, zirconium and/or bismuth) and salts thereof (e.g., bismuthsulfamate and/or bismuth lactate), bicyclic guanidine (as disclosed inU.S. patent application Ser. No. 11/835,600), or combinations thereof.

The electrodepositable coating composition disclosed herein is typicallysupplied as two components: (1) a main vehicle (“clear resin feed”) and(2) a grind vehicle (“pigment paste”). In general, (1) the main vehiclecomprises (a) a film-forming polymer (“an active hydrogen-containingionic salt group-containing resin”), (b) a crosslinking agent, and (c)any additional water-dispersible, non-pigmented components (e.g.,catalysts, hindered amine light stabilizers). In general, (2) the grindvehicle comprises (d) one or more pigments (e.g., titanium dioxide,carbon black), (e) a water-dispersible grind resin, which can be thesame or different from the film-forming polymer, and, optionally, (f)additives such as catalysts, antioxidants, biocides, defoamers,surfactants, wetting agents, dispersing aids, clays, hindered aminelight stabilizers, UV light absorbers and stabilizers, or combinationsthereof. An electrodeposition bath, which contains theelectrodepositable coating composition of the present invention, can beprepared by dispersing components (1) and (2) in an aqueous medium whichcomprises water and, usually, coalescing solvents. The (ii) yttriumand/or the (iii) silane, which are used in the electrodepositablecoating composition of the present invention, may be incorporated intothe main vehicle, the grind vehicle, or post-added to a bath that isprepared with components (1) and (2). Alternatively, components (1) and(2) may also be provided as a single component.

The electrodepositable coating composition described herein may beapplied alone or as part of a coating system that can be deposited ontoa number of different substrates. The coating system typically comprisesa number of coating layers. A coating layer is typically formed when acoating composition that is deposited onto the substrate issubstantially cured by methods known in the art (e.g., by thermalheating).

After the electrodepositable coating composition is cured, aprimer-surfacer coating composition is applied onto at least a portionof the electrodepositable coating composition. The primer-surfacercoating composition is typically applied to the electrodepositablecoating layer and cured prior to a subsequent coating composition beingapplied over the primer-surfacer coating composition.

The primer-surfacer layer that results from the primer-surfacer coatingcomposition serves to enhance chip resistance of the coating system aswell as aid in the appearance of subsequently applied layers (e.g.,color imparting coating composition and/or substantially clear coatingcomposition). As used herein, “primer-surfacer” refers to a primercomposition for use under a subsequently applied coating composition,and includes such materials as thermoplastic and/or crosslinking (e.g.,thermosetting) film-forming resins generally known in the art of organiccoating compositions. Suitable primers and primer-surfacer coatingcompositions include spray applied primers, as are known to thoseskilled in the art. Examples of suitable primers include severalavailable from PPG Industries, Inc., Pittsburgh, Pa., as DPX-1791,DPX-1804, DSPX-1537, GPXH-5379, OPP-2645, PCV-70118, and 1177-225A.Another suitable primer-surfacer coating composition that can beutilized in the present invention is the primer-surfacer described inU.S. patent application Ser. No. 11/773,482, which is incorporated inits entirety herein by reference.

It should be noted that in some embodiments, the primer-surfacer coatingcomposition is not used in the coating system. Therefore, a colorimparting basecoat coating composition can be applied directly onto thecured electrodepositable coating composition.

In some embodiments, a color imparting coating composition (hereinafter,“basecoat”) is deposited onto at least a portion of the primer surfacercoating layer (if present). Any basecoat coating composition known inthe art may be used in the present invention. It should be noted thatthese basecoat coating compositions typically comprise a colorant.

In certain embodiments, a substantially clear coating composition(hereinafter, “clearcoat”) is deposited onto at least a portion of thebasecoat coating layer. As used herein, a “substantially clear” coatinglayer is substantially transparent and not opaque. In certainembodiments, the substantially clear coating composition can comprise acolorant but not in an amount such as to render the clear coatingcomposition opaque (not substantially transparent) after it has beencured. Any clearcoat coating composition known in the art may be used inthe present invention. For example, the clearcoat coating compositionthat is described in U.S. Pat. Nos. 5,989,642, 6,245,855, 6,387,519, and7,005,472, which are incorporated in their entirety herein by reference,can be used in the coating system. In certain embodiments, thesubstantially clear coating composition can also comprise a particle,such as a silica particle, that is dispersed in the clearcoat coatingcomposition (such as at the surface of the clearcoat coating compositionafter curing).

One or more of the coating compositions described herein can comprisecolorants and/or other optional materials, which are known in the art offormulated surface coatings. As used herein, the term “colorant” meansany substance that imparts color and/or other opacity and/or othervisual effect to the composition. The colorant can be added to thecoating in any suitable form, such as discrete particles, dispersions,solutions and/or flakes (e.g., aluminum flakes). A single colorant or amixture of two or more colorants can be used in the coating compositiondescribed herein.

Example colorants include pigments, dyes and tints, such as those usedin the paint industry and/or listed in the Dry Color ManufacturersAssociation (DCMA), as well as special effect compositions. A colorantmay include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant can beorganic or inorganic and can be agglomerated or non-agglomerated.Colorants can be incorporated into the coatings by use of a grindvehicle, such as an acrylic grind vehicle, the use of which will befamiliar to one skilled in the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, disazo,naphthol AS, salt type (lakes), benzimidazolone, condensation, metalcomplex, isoindolinone, isoindoline and polycyclic phthalocyanine,quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo,anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments,diketo pyrrolo pyrrole red (“DPPBO red”), titanium dioxide, carbon blackand mixtures thereof. The terms “pigment” and “colored filler” can beused interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, perylene, aluminum and quinacridone.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5 mm.Example nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800, which is incorporated herein byreference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution). In order to minimizere-agglomeration of nanoparticles within the coating, a dispersion ofresin-coated nanoparticles can be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in whichdiscreet “composite microparticles”, which comprise a nanoparticle and aresin coating on the nanoparticle, is dispersed. Example dispersions ofresin-coated nanoparticles and methods for making them are identified inU.S. Patent Publication No. 2005/0287348, filed Jun. 24, 2004, U.S.Provisional Application No. 60/482,167 filed Jun. 24, 2003, and U.S.patent application Ser. No. 11/337,062, filed Jan. 20, 2006, which arealso incorporated herein by reference.

Example special effect compositions that may be used include pigmentsand/or compositions that produce one or more appearance effects such asreflectance, pearlescence, metallic sheen, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism and/or color-change. Additional special effectcompositions can provide other perceptible properties, such as opacityor texture. In a non-limiting embodiment, special effect compositionscan produce a color shift, such that the color of the coating changeswhen the coating is viewed at different angles. Example color effectcompositions are identified in U.S. Pat. No. 6,894,086, incorporatedherein by reference. Additional color effect compositions can includetransparent coated mica and/or synthetic mica, coated silica, coatedalumina, a transparent liquid crystal pigment, a liquid crystal coating,and/or any composition wherein interference results from a refractiveindex differential within the material and not because of the refractiveindex differential between the surface of the material and the air.

In certain non-limiting embodiments, a photosensitive composition and/orphotochromic composition, which reversibly alters its color when exposedto one or more light sources, can be used in the coating compositiondescribed herein. Photochromic and/or photosensitive compositions can beactivated by exposure to radiation of a specified wavelength. When thecomposition becomes excited, the molecular structure is changed and thealtered structure exhibits a new color that is different from theoriginal color of the composition. When the exposure to radiation isremoved, the photochromic and/or photosensitive composition can returnto a state of rest, in which the original color of the compositionreturns. In one non-limiting embodiment, the photochromic and/orphotosensitive composition can be colorless in a non-excited state andexhibit a color in an excited state. Full color-change can appear withinmilliseconds to several minutes, such as from 20 seconds to 60 seconds.Example photochromic and/or photosensitive compositions includephotochromic dyes.

In a non-limiting embodiment, the photosensitive composition and/orphotochromic composition can be associated with and/or at leastpartially bound to, such as by covalent bonding, a polymer and/orpolymeric materials of a polymerizable component. In contrast to somecoatings in which the photosensitive composition may migrate out of thecoating and crystallize into the substrate, the photosensitivecomposition and/or photochromic composition associated with and/or atleast partially bound to a polymer and/or polymerizable component inaccordance with a non-limiting embodiment of the present invention, haveminimal migration out of the coating. Example photosensitivecompositions and/or photochromic compositions and methods for makingthem are identified in U.S. patent application Ser. No. 10/892,919,filed Jul. 16, 2004.

In general, the colorant can be present in any amount sufficient toimpart the desired visual and/or color effect. The colorant may comprisefrom 1 to 65 weight percent of the present compositions, such as from 3to 40 weight percent or 5 to 35 weight percent, with weight percentbased on the total weight of the compositions.

The coating compositions can comprise other optional materials wellknown in the art of formulated surface coatings, such as plasticizers,anti-oxidants, hindered amine light stabilizers, UV light absorbers andstabilizers, surfactants, flow control agents, thixotropic agents suchas bentonite clay, pigments, fillers, organic cosolvents, catalysts,including phosphonic acids and other customary auxiliaries.

In addition to the materials described above, the coating compositioncan also comprise an organic solvent. Suitable organic solvents that canbe used in the coating composition include any of those listed in thepreceding paragraphs as well as butyl acetate, xylene, methyl ethylketone, or combinations thereof.

It will be further appreciated that one or more of the coatingcompositions that form the various coating layers described herein canbe either “one component” (“1K”), “two component” (“2K”), or evenmulti-component compositions. A 1K composition will be understood asreferring to a composition wherein all of the coating components aremaintained in the same container after manufacture, during storage, etc.A 2K composition or multi-component composition will be understood asreferring to a composition wherein various components are maintainedseparately until just prior to application. A 1K or 2K coatingcomposition can be applied to a substrate and cured by any conventionalmeans, such as by heating, forced air, and the like.

The coating compositions that form the various coating layers describedherein can be deposited or applied onto the substrate using anytechnique that is known in the art. For example, the coatingcompositions can be applied to the substrate by any of a variety ofmethods including, without limitation, spraying, brushing, dipping,and/or roll coating, among other methods. When a plurality of coatingcompositions are applied onto a substrate, it should be noted that onecoating composition may be applied onto at least a portion of anunderlying coating composition either after the underlying coatingcomposition has been cured or prior to the underlying coatingcomposition being cured. If the coating composition is applied onto anunderlying coating composition that has not been cured, both coatingcompositions may be cured simultaneously.

The coating compositions may be cured using any technique known in theart such as, without limitation, thermal energy, infrared, ionizing oractinic radiation, or by any combination thereof. In certainembodiments, the curing operation can be carried out at temperatures≧10° C. In other embodiments, the curing operation can be carried out attemperature ≦246° C. In certain embodiments, the curing operation cancarried out at temperatures ranging between any combination of values,which were recited in the preceding sentences, inclusive of the recitedvalues. For example, the curing operation can be carried out attemperatures ranging from 120° C.-150° C. It should be noted, however,that lower or higher temperatures may be used as necessary to activatethe curing mechanisms.

In certain embodiments, one or more of the coating compositionsdescribed herein is a low temperature, moisture curable coatingcompositions. As used herein, the term “low temperature, moisturecurable” refers to coating compositions that, following application to asubstrate, are capable of curing in the presence of ambient air, the airhaving a relative humidity of 10% to 100%, such as 25% to 80%, and atemperature in the range of −10° C. to 120° C., such as 5° C. to 80° C.,in some cases 10° C. to 60° C. and, in yet other cases, 15° C. to 40° C.

The dry film thickness of the coating layers described herein can rangefrom 0.1 micron to 500 microns. In other embodiments, the dry filmthickness can be ≦125 microns, such as ≦80 microns. For example, the dryfilm thickness can range from 15 microns to 60 microns.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the claims appended and any and all equivalents thereof.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications which are within the spirit and scopeof the invention, as defined by the appended claims.

EXAMPLES

Coating compositions, panels, and testing methods used in these Exampleswere prepared and described as follows:

Alkaline Cleaner 1: Chemkleen 2010LP/181ALP, a commercial alkalinecleaner available from PPG Industries, Inc.

Alkaline Cleaner 1A: Experimental alkaline cleaner with a compositionsimilar to Chemkleen 166HP, commercially available from PPG Industries,Inc.

Acid Cleaner 2—A citric acid cleaner prepared as follows. First, 468.4 gof anhydrous citric acid was dissolved in 18,000 g of water. Next, 103.4g of a commercial surfactant package, Chemkleen 171-12, was added to themixture. Finally, potassium hydroxide was added to the mixture to adjustthe pH of the resultant mixture to 4.5.

Pretreatment Composition 1: CHEMFOS 700, immersion applied tricationicZn phosphate (a commercial pretreatment product available from PPGIndustries, Inc.).

Electrodepositable Paint Composition 1: Enviro-prime® 7000P, a cationicelectrocoat commercially available from PPG Industries, Inc.

Electrodepositable Paint Composition 2: Yttrium-containingElectrodeposiable Paint prepared in accordance with Paint 4 in Table 1(paragraph [0074]) of U.S. patent application Ser. No. 12/693,626.)

Phosphated panels were purchased from ACT.

Test 1: 40 cycles of GM9540P (Cycle B)

Test 2: 24 hours in a cathodic disbondment test. The test involves ascribed panel submerged into a sodium sulfate solution where a currentof 10 mA is passed through the panel. After 24 hours, tape is used toremove delaminated paint and the width of the delaminated area ismeasured.

Comparative Results Experiment 1 Comparison of Corrosion Resistance onCleaned Panels Subsequently Coated with Electrodepositable CoatingComposition 1—Alkaline Cleaner 1 Vs. Acid Cleaner 2

Cold-rolled steel panels (ACT Panels) were cleaned using Cleaner 1 orCleaner 2, rinsed with deionized water, and dried using forced hot air.The panels were electrocoated in Electrodepositable Paint Composition 1and cured for 25 minutes @ 177° C. in an electric oven. The dry filmthickness was 0.0005-0.0010 inches. Samples were then scribed verticallyand placed in Test 1. Average scribe creep results are shown in Table 1below.

TABLE 1 Cleaner Avg Scribe Creep (mm) #1 - 2′ Spray 18.7 #2 - 4′ Spray7.6

Experiment 2 Comparison of Corrosion Resistance on Cleaned PanelsSubsequently Coated with Electrodepostable Coating Composition2—Alkaline Cleaner 1A Vs. Acid Cleaner 2

Cold-rolled steel panels (ACT Panels) were cleaned using AlkalineCleaner 1A or Acid Cleaner 2, rinsed with deionized water, and driedusing forced hot air. The panels were electrocoated inElectrodepositable Paint Composition 2 and cured for 25 minutes @ 177°C. in an electric oven. The dry film thickness was 0.0005-0.0010 inches.Samples were then scribed vertically and placed in Test 1. Averagescribe creep results are shown in Table 2 below:

TABLE 2 Cleaner Avg Scribe Creep (mm) #1A - 2′ Immersion 9.5 #2 - 4′Spray 3.3

Experiment 3 Comparison of Yttrium Deposition on Cleaned Panels—AlkalineCleaner 1A Alone Vs. Alkaline Cleaner 1A Followed by Acid Cleaner 2

Cold-rolled steel panels (ACT Panels) were cleaned using AlkalineCleaner 1A alone, or Alkaline Cleaner 1A followed by Acid Cleaner 2, andrinsed with deionized water. The panels were then placed in a solutionof yttrium sulfamate (800 ppm yttrium) buffered to a pH of 5.5. 80 mA ofcurrent was passed through the solution for 2 minutes at roomtemperature. Panels were then rinsed with deionized water and driedusing forced air. After drying, the amount of yttrium deposited on thepanels was measured by wave-dispersive X-ray fluorescence. The resultsare shown in Table 3 below:

TABLE 3 Cleaner #1A Cleaner #2 Wt % Y 2′ Spray — 0.82 1′ Spray 2′ Spray1.5

Experiment 4 Comparison of Corrosion Resistance on Cleaned PanelsSubsequently Coated with Electrodepositable Coating Composition2—Cleaner 1A Vs. Cleaner 1A Followed by Cleaner 2 Vs. Cleaner 2 Followedby Cleaner 1A—Ecoated Panels (with Corrosion Inhibitor)

Cold-rolled steel panels (ACT Panels) were cleaned using AlkalineCleaner 1A, Alkaline Cleaner 1A followed by Acid Cleaner 2, or AcidCleaner 2 followed by Alkaline Cleaner 1A, and then rinsed withdeionized water. Panels were then dried using forced air. After drying,the panels were electrocoated in Electrodepositable Paint Composition 2and cured for 25 minutes @ 177° C. in an electric oven. The dry filmthickness was 0.0005-0.0010 inches.

Panels with Pretreatment 1 were purchased from ACT and electrocoatedwith Electrodepositable Paint Composition 1 for comparison.

Samples were then scribed vertically and placed in Test 2. The resultsare shown Table 4 below:

TABLE 4 Scribe Creep Step 1 Step 2 (mm) Cleaner #1A - 2′ Spray — 5.52Cleaner #1A - 30 sec Spray Cleaner #2 - 3′ Spray 3.03 Cleaner #2 - 3′Spray Cleaner #1A - 30 sec Spray 3.00 Phosphate (Pretreatment #1) 5.34

We claim:
 1. A method comprising: (a) contacting a substrate with anacid; and then (b) contacting the substrate with an electrodepositablecoating composition comprising (i) a film-forming polymer; and (ii) acorrosion inhibitor; with the proviso that the method does not comprisecontacting the substrate with a pretreatment composition prior to step(b).
 2. The method of claim 1, wherein said corrosion inhibitorcomprises a rare earth metal, a lanthanide, or combinations thereof. 3.The method of claim 1, wherein said corrosion inhibitor comprises asource of yttrium.
 4. The method of claim 3, wherein said source ofyttrium comprises an yttrium compound.
 5. The method of claim 1, whereinsaid corrosion inhibitor comprises a source of cerium.
 6. The method ofclaim 1, wherein said source of cerium comprises a cerium compound. 7.The method of claim 1, wherein said corrosion inhibitor comprises asource of yttrium and a source of cerium.
 8. The method of claim 1,wherein said electrodepositable coating composition further comprises(iii) a silane that does not contain an ethylenically unsaturated doublebond
 9. The method of claim 1, wherein said acid comprises an organicacid.
 10. The method of claim 1, wherein said acid comprises a mineralacid.
 11. The method of claim 1, wherein said acid comprises an organicacid, a mineral acid or mixtures thereof.
 12. The method of claim 9,wherein said organic acid comprises a carboxylic acid.
 13. The method ofclaim 9, wherein said organic acid comprises citric acid.
 14. The methodof claim 1 further comprising (c) contacting the substrate with analkaline cleaner prior to steps (a) and (b).
 15. The method of claim 1further comprising (c) contacting the substrate with an alkaline cleanerprior to step (b) and after step (a).
 16. A coated substrate formed inaccordance with the method of claim
 1. 17. A coated substrate formed inaccordance with the method of claim
 8. 18. A method for coating asubstrate comprising: (a) contacting the substrate with an acid; (b)contacting the substrate with an alkaline cleaner; and then (c)contacting the substrate with an electrodepositable coating compositioncomprising (i) a film-forming polymer; and (ii) a corrosion inhibitor;with the proviso that the method does not comprise contacting thesubstrate with a pretreatment composition prior to step (b).
 19. Themethod of claim 1, wherein said corrosion inhibitor comprises a rareearth metal, a lanthanide, or combinations thereof.
 20. A coatedsubstrate formed in accordance with the method of claim 19.